Current interrupting circuit



1949 A. c. VIAN DORSTEN 2,490,552

CURRENT INTERRUPTING CIRCUIT Filed July 16, 1946 CONTROL CIRCUIT CONTROL CIRCUIT FIG INVENTOR ADRIANUS CORNELIS VAN DQRSTEN BY 7 4 ATTORNEY.

Patented Dec. 6, 1949 Adria-nus Cornelis van Dorsten,

Eindhoven,

Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn, as

trustee Application July 16, 1946, Serial No. 684,086 In the Netherlands January 26, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires January 26, 1963 It is known that the difliculties experienced in' interrupting an electric current by means of a gasor vapour-filled dischargetube, capable of being extinguished, increase as the voltage across the tube after extinction is increased. This is due to the fact that, as a result of the subsisting residual ionization, the risk of re-ignition of the tube and of the production of a glow discharge is also greater with an increase in voltage. This holds true both in regard to tubes utilizing a voltage applied to a control electrode to aid extinction and tubes that are extinguished by means of a voltage impulse on the anode and/or an auxiliary anode.

In cases occurring in practice, for instance in the transmission of direct current energy having a high voltage and a high power, in which case this energy is to be converted at the end of the line into alternating-current energy whose voltage is n times lower, voltages of some tens of kilovolts to hundreds of kilovolts and higher and currents of several amperes to tens of amperes are concerned.

The present invention has for its purpose to meet the above drawbacks in regard to the extinction of a converting tube.

To this end, in the device according to the invention, a high-vacuum tube (auxiliary tube) capable of being controlled is connected in parallel with the discharge tube to be extinguished (main tube), which auxiliary tube at the moment of extinction is capable of taking over practically the whole current of the main tube for a short time at such a lowvoltage that undesired reignition of the main tube, due to residual ionization in the main tube, cannot occur. When the current is to be interrupted the auxiliary tube is made conductive just prior to the moment of extinction of the main tube, and is kept conductive for such a, time, of the order of magnitude of 10- to 10" sec., that ole-ionization has sufficiently progressed in the main tube to prevent re-ignition.

In order that the invention may be clearly understood and readily carried into efiectit will now be described more fully with'reierence. to the accompanying drawing, in which one form of construction is represented by way of example.

Fig. 1 represents the circuit arrangement of a device in which the main tube is connected in series with a load to a direct voltage supply.

Fig. 2 illustrates the voltage set up at the main tube and the auxiliary tube during operation. as a function of time.

4 Claims. (Cl. 315-340) 3 is a circuit diagram of an alternative embodiment of the invention.

In Fig. 1 the reference number I designates the terminals of a supply of direct voltage of, say,

' several tens of kilovolts with which are connected in series a load 2 and a discharge tube 3 having a mercur cathode 4 and an anode 5. The tube is equipped with an ignition electrode 5 for which is chosen in the present case a semi-conductor continuously immersed in the cathode mercury.

In parallel with the (main) tube 3 is connected a high vacuum triode (auxiliary tube) 1 having an incandescent cathode 8, a grid 9 and an anode A device for extinguishing this tube is also connected in parallel with the main tube. In the present example this device consists of the seriesconnection of an extinguishing condenser 12 connected to a direct voltage supply H, a gasor vapour-filled tube l3 and a smaller condenser I4. The tube I3 is equipped with an anode l5 and a mercury cathode I6 and can be ignited, similarly to the main tube, through a voltage impulse by means of an auxiliary electrode ll im- W mersed in the mercury and consisting of a semiconductor. The grid 9 and the starting electrodes 6 and I! are connected to a control circuit, indicated by a block in the drawing. Conventional types of control circuits for applying the desired voltage pulses at the desired times are known and may be employed.

The operation of this circuit is as follows;

set up at the grid 9 of the tube 1 is made less negative, e. g. positive, in such a manner that the tube becomes conductive and is capable of taking over for a short time substantially the full load current' of the tube at an anode voltage of the order of magnitude of 500 to 1000 volts. As long, however, as the tube 3 has not been extinguished, so that the anode voltage of the tube 1 still corresponds to the operating voltage of the tube 3, by far the greater part Of the current will pass through tube 3.

After that the discharge in the tube 3 is extinguished which takes place by ignition of the 3 tube l3 by means of the ignition electrode II. In this case the extinguishing condenser l2 previously charged, which is connected with the negative side to the tube l3, discharges through the tube [3, and the initially uncharged condenser Hi charges through the tube 3 as a result of which the potential of the anode 5 is re duced for a short time relatively tothat of the.

cathode or even becomes negative in such a manner that the discharge is extinguished.

Since, however, the tube 1, which has previously been made conductive, is connected in parallel with the tube 3 the full mains voltage does not directly return to the tube 3-in thisv state of reduced breakdown security, but the tube 3 is first exposed to the much lower anode voltage of the tube 7 of, say, 500 to 1000 volts. Despite the subsisting, though decreasing, residual ionization in the tube after extinction, re-ignition or. other disturbances in the state of the tube are not to be feared at this voltage. Only after. the de-ionization has progressedto a sufiicient. de: gree, which requires a. time. of. the order of 10 to 10- sec. and the tube 3 has acquired again its full voltage security, theipassage of .cur-.

rent through the tube 1 is blocked andthe full mains voltage returns to the .tubes3and T. The condenser M serves to absorb this voltage for the greater part in theparallel branch, so that only a fraction thereof is set up at the condenser I2.

In the present state of the art the. conditions imposed on the high-vacuum tube can be satisfied for a-generous range of voltages and currents. It is not necessary to make use of a tube with grid-control. One'may also-usea tubewith magnetic .control, which has theadvantage that the.

grid losses are avoided ,andthe control energyis materially reduced.-

Fig. 2 illustrates thevoltage variation, of thetubes 3 and 1- as a function oftime. ti represents the time during which the tube.3- and,

shortly before theend also the. tube-1, is con. ductive, s thatthevoltage E1 setupat the tubes corresponds to the operating voltage of the tube 3. During t2 the tube. 3 is extinguished. and the voltage E2 set up at the tubes corresponds to the anode voltage of the tube 1. 222 is of the order of'magnitude of 10- -to 10 'sec. in such manner that in this time the .residual'ionization disappears in the tube 3. The tube 1 is now blocked so that during t3 the full mainsvoltage E3 returns to the tubes. After that a new cycle begins with the ignition-of the tube 3-, as app ars from Fig. 2'.

From Fig. 2 it also appears that by periodical:

ignition and extinction, and blocking respectively of the tubes 3 and 'lthe circuit according to theinvention is adapted, inprinciple, for use as an alternating current converter, its load being e. g; a transformer for converting-a highdirect voltage into a lower alternatingvoltage; In this, case. the periodicity in the succeeding variationsinv condition of the tubes isto bechosenin accord.-. ance with the frequency'of the; generated alter-.

nating voltage.

As an alternative, however, the circuit of the invention may be used for switching on and off alternating currents which may or may not be periodic. the circuit of Fig. 3. A source 20 of alternating current has terminals 20' and 2|!" and a load 22 one side of which is connected to the terminal 28". A mercury vapor tube 23 and high vacuum tube 2'l are connected in parallel; that is. with their anode terminals connected together and:-

Such an alternative is'illustrated by.

their cathodes connected together. The anodes are connected to terminal 20. Another mercury vapor tube 28 and a high vacuum tube 30 are also connected in parallel with. their anode terminals connected to the other side of load 22 and to the cathodes of tubes 23 and 27. The anode terminals of tubes 23 and 21 are connected to the cathode terminals of tubes 28 and 30 as shown. The tubes 27 and 30 are controlled respectively by the magnetic fields of coil 21a and and coil 33a which are connected to the control circuit. Mercury vapor tubes 23 and 28 have mercury pool cathodes and control electrodes 23a and 2811 respectively which are also connected to the control circuit. Tubes 33 and 34 are mercury vapor tubes having mercury pool cathodes. The anode of tube 33 is connected to a condenser 35 which is connected to the anode of. tube 23. The cathode of tube 33 is connected to a condenser 36 across which is a direct current source. with thepolarity shown. The other side. of, the. condenser, 36; is. connected to. thev cathode .of tube 23. The anode-of tube..34 is. con nected to a condenser 38, the. other. side. of. which other side of which is. connectedto the cathode of tube 28. Acrosscondenser. isa direct our.-

rent-source withthepolarity shown. The control electrodes 33a and34a. of, tubes 33 and 34.repectively are connected to. the control. circuit.

As conventional forms, of the. control circuit are. known. to the art, the. circuit is not. completely. illustrated. The tubes 23 and 28 of Fig. 3 may .be

otthe same typeas. tube 3. of. Fig. 1 and the tubes .33 and 34 ofFfig. 3.-may beofthe same typ as tubev 13. of Fig. 1. Tubes21 and 3U-are. high. vacuum tubes controlled by the. magnetic held. of

coils. 21a and. 30a. In operation, the. circuit 9.1?

lows currents of alternating. polarity to pass through the load 22. For example, thesource 20 may. have a. sinusoidal voltage form and the current passing through the load 22 maybe controlled. to. permit passage of the current. during any desired phaseperiodof eachhalf cycle. The

coils 21a and 30a receive pulsesfrom. the control circuit in such a manner. that when thetube 23 or.28-is.to be extinguished, the tube 21 or 30, as the case may be, conducts very heavily for a.

-' timeof the order of 10a or.10* seconds to permit substantially complete deionization of tubes 2,3.and 28. The functions of tubes 33 and 34 andtheir: associated condensers and the direct current sources. across the condensers 3t and 40 is analogous to the function of. tube l3 and its associatedcircuit in Fig. 1. and will be understood from what has been saidhereinbefore.

What I claim is: 1. An

inga vapor-filleddischarge tube-having a cathode and an anode, a load impedance connected in series with the cathode and anode of said tube. and a source of electric power, an arc-extinguish:-

ing deviceconnectedin parallel. with said vaporfilled dischargetube, and means to prevent. re.-

ignition of saidtube. said latter means comprising.

ele trical. circuit arran ement commie-- ing a vapor-filled discharge tube having a cathode, an ignition electrode and an anode, a load impedance connected in series with the cathode and anode of said tube and a source of electric power, means coupled to said ignition electrode to periodically ignite said tube, an arc-extinguishing device connected in parallel with said vapor-filled discharge tube to extinguish said tube, and means to prevent re-ignition of said tube immediately following the extinction thereof, said latter means comprisin a high vacuum electron discharge tube having a cathode and an anode connected in parallel with said vapor-filled tube and having a control grid, and a source of a control potential coupled to said control grid to render said high vacuum tube conductive for a period of the order of 10 seconds during the period of extinction of said vapor-filled tube.

3. An electrical circuit arrangement comprising a first vapor-filled discharge tube having a cathode, an ignition electrode and an anode, a load impedance connected in series with the cathode and anode of said tube and a source of electric power, a control circuit coupled to said ignition electrode to periodically ignite said tube, a series circuit comprising a second vapor-filled discharge tube having an anode, a cathode and an ignition electrode and first and second capacitors, means to connect said series circuit in parallel with said first discharge tube, means to connect a charging potential to one of said capacitors, a control circuit coupled to the ignition electrode of said second discharge tube to ignite the same and extinguish said first discharge tube, and means to prevent reignition of said first tube immediately following the extinction thereof, said latter means comprising a high vacuum electron discharge tube having a cathode and an anode connected in parallel with said first discharge tube and having a control grid, and a source of a control potential coupled to said control grid to render said high vacuum tube conductive for a period of the order of 10* seconds during the period of extinction of said first discharge tube.

4. An electrical circuit arrangement comprising a first vapor-filled discharge tube having a cathode, an ignition electrode and an anode, a load impedance connected in series with the cathode and anode of said tube and a source of electric power, a second vapor-filled discharge tube having a cathode, an ignition electrode and an anode, means to connect the anode of said first tube to the cathode of said second tube and the cathode of said first tube to the anode of said second tube, a control circuit comprising means coupled to said ignition electrodes to periodically ignite said tubes selectively, first and second arcextinguishing devices connected in parallel with said first and second vapor-filled discharge tubes respectively to extinguish said tubes, and means to prevent re-ignition of said tubes immediately following the extinction thereof, said latter means comprising a first high vacuum electron discharge tube having a cathode and an anode connected in parallel with said first vapor-filled tube and having a control element, a second high vacuum electron discharge tube having a cathode and an anode connected in parallel with said second vapor-filled tube and having a control element, and a source of control voltage derived from said control circuit coupled to said control elements to render said high vacuum tubes conductive substantially during the period of extinction of the associated vapor-filled discharge tube.

ADRIANUS CORNELIS VAN DORSTEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,691,395 Langmuir Nov. 13, 1928 2,147,472 Ulrey Feb. 14, 1939 2,221,569 Berkey Nov. 12, 1940 

